<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    var s = new String('hello');
    console.log(s);
    document.write(s);
    var arr = s.split('');
    // arr  Array  object
    //s String object
    if (typeof arr == 'object' && arr instanceof Array){
        alert('arr是数组')
    }
    if (typeof s == 'object' && s instanceof String){
        alert('s是字符串对象')
    }

    var username = 'frank';
</script>
</body>
</html>